High-frequency electrical filter for use in wave guides



March 27, 1951 GUTTON ET AL 2,546,742

HIGH-FREQUENCY ELECTRICAL FILTER FOR USE IN WAVE GUIDES Filed April 11, 1947 3 SheetsSheet 1 I F" F" F" ImvENToRs HENR/ GUTTON ANTOINE JEAN ORTt/Sl AGENTS March 27, 1951 GUT-TON ET AL 2,546,742

HIGH-FREQUENCY ELECTRICAL FILTER FOR USE IN WAVE GUIDES Filed April 11, 1947 4 3 Sheets-Sheet 2 INVENTOR5 HENRI CTUTTON AN OINE JEAN oRTvs\ ACTENTJ March 27, 11951 H. GUTTON ET AL 2346 742 HIGH-FREQUENCY ELECTRICAL FILTER FOR USE IN WAVE GUIDES Filed April 11, 1947 3 Sheets-Sheet 3 .ZNVENTORS 7 HENRI Qu -raq I Amome D'EAN saws Acfea-rs Patented Mar. 27, 1951 HIGH-FREQUENCY ELECTRICAL FILTER FOR USE IN WAVE GUIDES Henri Gutton and Antoine Jean ()rtusi, Paris, France, assignors to Compagnie Generale De Telegraphic Sans Fil, a corporation of France Application April 11, 1947, Serial No. 740,844 In France June 2,-1945 Section 1, Public Law 690, August 8, 1946 Patent expires June 2, 1965 I 6 Claims. (Cl. 178-44) This invention relates to high frequency electrical filters for use in wave guides and more particularly though not exclusively to band pass filters for use on decimetre waves in a wave guide employed, for example, for connecting a transmitter with a radiating horn. An arrangement in accordance with this invention comprises at least two resonators coupled in the guide by one or more spaces. 7

For a certain critical coupling given by a resonant space between two resonators the trans mission curve'of an assembly thus constituted presents aflattoppedcurve characteristic of a band pass filter.

An arrangement in accordance with this invention can, however, comprise more than two resonators inter-coupled by intervening adjustable spaces and be arranged to give a transmis sion curveofalmost any form desired.

The specific description hereinafter given is limited for the sake of simplicity to the case of two identical coupled resonators but the invention is not limited to this case. The invention is illustrated in and further explained in connection with the accompanying drawings, in which Figure 1 is a diagrammatic showing of the wave guide having two spaced cavity resonators;

Figure 1a is a view of the same wave guide partly in perspective and partly in section;

Figure 2 shows a transmission curve of each resonator taken alone;

Figure 3a to Figure 3d are diagrams of transmission curves based on varying relations of length of the resonator chambers and of the space therebetween;

Figure 4 is a view partly in diagram and partly in section of an adjustable metallic insert;

Figure 5 shows a typical curve connecting the length values of the resonator and the intervening space;

Figure 6 is a transverse sectional view of a sliding arrangement for the resonator chamber; and

Figure 7 is a longitudinal sectional view of the arrangement shown in Figure 6.

Referring to Fig. 1, R1 and R2 are two identical resonators formed with apertures F1, F'1 and FaF'z, and arranged in a wave guide C with an adjustable space E between them. Each resonator, considered alone, has a transmission curve of the form represented in Fig. 2, where co-eificients of transmission T are plotted as ordinates against frequency f. flhe width of the band passed by such a resonator may be retransmission is of the form illustrated by Fig 3a; if I is equal to the curve of transmission is of the form illus trated in Fig. 32;; if Z is substantially equal to the curve of transmission isas represented by Fig. 30; while for values of Z notably greater than 20 the curve of transmission reverts to a form as shown in Fig. 3d.

The case were Z=l0 is that of three like resonators arranged end to end and this case may be useful as a means for transmitting three equally separated frequencies. But the case with which the present invention is primarily concerned in practice is that corresponding to Fig. 3c, 1. e. the band pass case.

In practice a band pass filter in accordance with this invention may be made and adjusted without touching the resonators R1 and R2 once positioned, for the length I may be, in effect, varied (without actually moving R1 or R2) by providing one or more adjustable metallic inserts such as rods or screws V (Fig. 4) positioned with respect to the apertures F'1 or F2 of the resonators R1 and R2 at a distance equal to one quarter of the wave length A in the guide. The

effective length of the space is then a function of the extent of entry of the insert or inserts V and accordingly a desired modification of the transmission curve of the arrangement is obtainable by adjusting the said inserts. Fig. 5 is a typical curve connecting values of ZZ0 expressed in centimetres as a function of the extent of entry e (also expressed in centimetres) for a rectangular sectioned guide 5 cm. x 16 cm. operating on a wave length (A) of 20 cm.

To facilitate adjustment of the resonators where movableresonators are required they may be constituted by suitably sectioned boxes (corresponding with the wave guide section) of dimension a little less than the interior dimensions of the guide so that they can slide easily therein, electrical contact with the guide being ensured by suitable metallic contacts and handles sliding in longitudinal slots formed in the guide wall being provided. The metallic contacts should be located along nodal lines of the electric current circulating in the plane of the section of the guide. The regulating rod or other insert of each resonator is situated in a transverse plane different from that of the handles thereof and also slides freely in a wall slot formed in the guide.

Fig. 6 shows in transverse sectional view and Fig. '7 in longitudinal sectional view a sliding arrangement of the nature described in the last paragraph for the case of a rectangular guide dealing with an H01 wave. In these figures E represents a box which slides in the guide G between friction contacts Q, P, P represent the handles fixed to E and which slide in longitudinal slots L in the Walls of the guide G and V represents the tuning insert of the resonator.

What we claim is:

l. A filter device comprising, in the interior of a wave guide provided with longitudinal slots constructed in its wall, two cavity resonator elements positioned in series in said guide and tuned to the same frequency, one of said resonator elements comprising a box slidable in the interior of the guide and provided with contacts for establishing electrical contact with the guide and with handles extending out from the guide through said slots.

2. A filter device comprising, in the interior of a guide provided with longitudinal slots constructed in its walls, two cavity resonator ele' ments positioned in series in said guide and tuned to the same frequency, one of said resonator elements comprising a box slidable in the interior of the guide and provided with contacts for establishing electrical contact with the guideand with handles extending out from the guide through said slots, a conductive rod positioned in the interior of said guide in the space between said resonators, and means connected to the 4 guide for adjusting the depth of entry of said rod into the guide.

3. A filter device according to claim 1 in which said cavity resonators are mutually positioned at a distance substantially equal to lo being the length of one of said cavity resonators and i being the length of the wave in the guide. 4. A filter device according to claim 2 in which said resonators are mutually positioned at a distance substantially equal to Zn being the length of one of said cavity resonators and A being the length of a wave in the guide.

5. A band-pass filter device comprising, in the interior of a wave guide, two cavity resonator elements positioned in series in said guide and tuned to the same frequency, one of said resonator elements being a slidable element so as to vary the physical distance separating the two' resonators from one another and to thereby adjust the width of the pass band of said filter.

6. A band-pass filter device as claimed in cl'aini' 5 including a conductive rod positioned in the: interior of said guide in the space between said resonators, and means connected to the guide for adjusting the depth of entry of said rod into the guide. 4 V

HENRI GUTTON. ANTOINE JEAN ORTUSI'.

REFERENCES CITED UNITED STATES PATENTS Date . Number Name 2,407,267 Ginzton Sept. 10, 1946' 2,432,093 Fox Dec. 9, 1947 2,434,646

Fox Jan. 20, 194$ 

